解方程-x^3/72+x^2/18-2x/9-8/3=0
问题描述：
解方程-x^3/72+x^2/18-2x/9-8/3=0
答
(x+1/x)²=9
x²+2×x×1/x+1/x²=9
x²+2+1/x²=9
x²+1/x²=7
(x-1/x)²
=x²-2×x×1/x+1/x²
=x²-2+1/x²
=7-2
=5
答
x³-4x²+16x+192=0x³+4x²-8x²+16x+192=0x²(x+4)-8(x²-2x-24)=0x²(x+4)-8(x+4)(x-6)=0(x+4)(x²-8x+48)=0x²-8x+48=0无解x=-4